Solenoid-actuated pilot valve

ABSTRACT

An improved solenoid-actuated pilot valve having a valve core of magnetic material and formed with an axial central bore and a plurality of offset radial discharge ports for rotating the core slightly each time it is raised off its seat. An improved splitshell housing for the solenoid is also provided to establish an efficient flux-return path for the magnetic field created by the solenoid.

United States Patent 2,359,017 9/1944 Balsiger 137/332 2,366,412 1/1945Lambert 251/139X 2,616,955 11/1952 Dube et a1. 25l/139X 3,125,321 3/1964Van Domelen... 251/139 1,587,921 6/1926 Ray 251/139X 3,340,773 9/1967Franz 137/596.l7X

Primary ExaminerHenry T. Klinksiek AttorneyFrank R. Thienpont ABSTRACT:An improved solenoid-actuated pilot valve having a valve core ofmagnetic material and formed with an axial central bore and a pluralityof offset radial discharge ports for rotating the core slightly eachtime it is raised off its seat. An improved split-shell housing for thesolenoid is also provided to establish an efficient flux-return path forthe magnetic field created by the solenoid.

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( Jxu Mil QR PATENTED 1111231111 7' SHEET 1 OF 2 PATENTEU FEB2-3197|3565111 sum 2 [IF 2 SOLENOID-ACTUATED PILOT VALVE This invention relatesto valves and valve actuation and more particularly to electricallyactuated valves of the solenoid type wherein the solenoid surrounds thevalve port or flow line.

Solenoid actuated valves are well known in the art and have manydifferent configurations. In nearly all cases, there is a magneticallyactuated valve member which forms a fluidtight seal against a valveseat. Through repeated use, either the valve member or the seat maybecome distorted or worn so that they no longer provide an effectiveseal.

It is an object of this invention to provide an improvedsolenoid-operated pilot valve for controlling the flow of fluid underpressure and having a magnetically movable valve core adapted to form afluidtight seal against a valve seat and including means for imparting aslight rotational motion to the valve core each time it is lifted awayfrom the valve seat.

It is also an object to provide a split sleeve of high-permeabilitymagnetic material surrounding the valve core and effective to provide aslight hammerlike impact to the valve core each time the solenoid isactuated to lift the core away from the seat or to reseat the core. Thecombination of the rotation of the valve core on each actuation of thesolenoid and the light hammerlike blows tends to form the valve seat toconform to the shape of the valve core so that a perfect fluidtight sealis ensured even after prolonged use.

It is still another object to provide an improved split-shell housing ofmagnetic material for enclosing the solenoid and ensuring an efiicientflux return path for the field created by the solenoid. The housing issplit along the axis of the valve and parallel with the lines of flux sothat there is no open circuit or gap in the flux path.

Other objects and advantages of theinvention will become more readilyapparent when considered in connection with the accompanying drawings inwhich:

FIG. 1 is a longitudinal sectional view of the pilot valve of thepresent invention;

FIG. 2 is a sectional view taken on line 2-2 of FIG. 1;

FIG. 3 is a side view showing the split solenoid housing;

FIG. 4 is a longitudinal sectional view of a valve core having ofisetradial ports;

FIG. 5 is an enlarged sectional view taken on line 5-5 of FIG. 4 andshowing the orientation of the offset radial ports;

FIG. 6 is a sectional view of a valve core having true radial ports andan inverted cup-type of valve tip;

FIG. 6A is a bottom view of the inverted cup valve tip of FIG. 6.

FIG. 7 is an enlarged sectional view taken on line 7-7 of FIG. 6;

FIG. 8 is a modified form of valve core having a split-sleeve impactform;

FIG. 9 is a longitudinal sectional view of a hydraulically actuatedshiftable control valve adapted for use with the pilot valve of FIG. 1;and

FIG. 10 is a coiled compression spring used in the pilot valves.

The improved solenoid-operated pilot-control valve of the presentinvention is herein described and shown on the accompanying drawingswherein like characters-of-reference designate like parts in the severalviews. I

The control valve assembly shown in FIG. 1 commonly known as a three-wayvalve, is designated generally by the numeral l0 and includes asolenoid-actuated inlet control valve 11 and a solenoid-actuated outletcontrol valve 12.

The valve 11 alone is commonly known as a two-way valve and comprises acylindrical tube 15 of nonmagnetic material, a valve core 16 slidablydisposed within the tube 15, a solenoid coil 17 surrounding the tube 15,and a split-shell housing 18 surrounding the solenoid coil 17. Acylindrical fitting 20 having an axially extending bore 21 therethroughand external threads 22 forms a fluidtight seal with the tube 15 at 23.An adapter plug or fitting 24 having an axially extending bore 25thercthrough is threaded into the bore 21 at 26. The bore 25 opens intothe bore 21 and, collectively, they provide an inlet port 30 to thevalve 11. The bore 21 is reduced in diameter at 31 and opens into acylindrical cavity or bore 32 defined by the inner wall of the tube 15.The valve core 16 is constrained to move longitudinally within the bore32. A coiled compression spring 33 such as is shown in FIG. 10 isdisposed within the bore 21 and has a longitudinally extending shank 34which extends through the bore 31 and acts against the bottom of fluidpassage of core 16. 1

The fitting 20 has formed in its lower end a circular groove 35 aroundthe bore 31 for retaining a copper shade ring 36. When the solenoid 17is energized from an AC source, the lines of magnetic flux cuttingacross the ring 36 generate an e.m.f. and cause a current to flowtherein. The current flowing in the coil 17 creates a magnetic fluxfield counter to the applied field. The shade ring 36 thereby functionsto dampen rapid changes in flux in close proximity to the core 16 andtends to minimize unwanted vibration of the core 16.

A flanged cylindrical plug 37 is press-fitted into the lower end of tube15 and is adapted to form a fluid tight seal therewith. The plug 37 isformed with a central bore or orifice 38 which functions as a valve seatfor the tip 39 of core 16. The cylindrical tube 15, the fitting 20, andthe plug 37 thus form a tube assembly in which the valve core 16 isslidably disposed. The plug 37 may be made of soft metal but could alsobe made of a plastic such as Teflon depending on the valve application.The plug 37 also may be formed with a bore in its upper end to receivereplaceable valve seats to accommodate one of several valve tips'such,for example, as are herein illustrated. The bore 38 and conduitsconnected to it collectively constitute an outlet port 40 for the valve11. The tube 15 is shown as flanged or flared outwardly at 41 andreceives the circular flanged edge 42 of plug 37. The flared edge 41also cooperates with an internally tapered nut 43 for mounting the valve11 on a mounting block 44.

The block 44 is generally cylindrical in shape and is formed withenlarged threaded axial bores 45 and 46. The bore 45 is formed withinternal threads 47 and a flat bottom 48. The threads 47 are cut to meshwith external threads 49 formed on the nut 43. The nut 43 is also formedwith notches 50 and 51 apart and adapted to receive a spanner wrench(not shown) for tightening the nut 43. When the nut 43 is tightenedsecurely, the end of tube 15 formsa fluidtight seal with a gasket 48adisposed on the bottom 48 of the bore 45.

Referring to FIG. 2, the block 44 is formed with an axial port 52 and aradial bore or channel 54. The port 52 registers with the bore 38 andthe channel 54 and the latter directs fluid to the fluid pressureresponsive member to be controlled. A standard hydraulic fitting 56 isshown connected to the bore 54. The block 44 is formed with an integralbase or mounting bracket for mounting the valve assembly on a stationarymember.

The solenoid 17 may be a conventional coil of the proper number of turnsand of the physical dimensions and wire size required for thisapplication. The solenoid l7 surrounds the tube 15 and is sandwichedbetween steel washers 60 and 61. The washers 60 and 61 help to retainand protect the solenoid 17 within the housing 18 and also provide aportion of the flux-return path for the magnetic field created by thesolenoid 17 when energized. The lines of flux, by definition, areparallel to the axis of the solenoids.

Referring now to FIG. 3, the housing 18 is seen to comprise two halves63 and 64 split along a longitudinal axis and which, when joinedtogether, form a complete shell generally cylindrical in form. Thehalf-shells 63 and 64 are made of suitable magnetic material and areflared outwardly at 65, 66, 67 and 68. In assembling the housing 18around the coil 17, the flared portions 67 and 68 form a circular shroudin close proximity to the tube 15, and this shroud is received within acylindrical recess 69 formed in nut 43. As the two halved 63 and 64 arebrought together, the flared portions 65 and 66 also form a circularshroud enclosing the tube 15. A self-locking circular nut 70, preferablymade of aluminum or other nonmagnetic material, is threaded on to thethreads 22 formed on the exterior of the fitting 20 and is adapted to behand tightened. The nut 70 is also formed with an internal cylindricalrecess 71 for receiving the shroud created by the flared portions 65 and66. Advancing the nut 70 forces the two halves 63 and 64 into closephysical contact. Theshell-half 63 is formed with an out- Referring nowto FIGS. 4, 5, 6, 7 and 8, several different I forms and views ofportions of valve cores 16 are illustrated. Referring particularly toFIG. 4, the valve core 16 is seen to comprise a generally elongatedcylindrical body 80 formed with an axial central bore 81, a plurality ofradially offset outlet ports 82 communicating with the bore 81, and avalve tip 39. The tip 39 may be formed of hardened material and isproperly tapered to flt closely with the valve seat 38. During assemblya light blow on the valve core with a rod inserted into the assemblywill enable the valve tip 39 to form its own mating seat in the plug 37or in the replaceable valve seat material disposed in the plug 37.

It is contemplated that in operation, the fluid to be controlled passesthrough the bore 81 and is discharged outwardly through the offsetoutlet ports 82 when the core 16 is raised off its seat under the forceof the actuated solenoid 17. The momentum of the fluid dischargedthrough the ports 82 imparts a slight turning moment to the core 16.Repeated actuation of the solenoid l7 and the light hammer blowsimparted to the seat 38 whenever the valve tip 39 reseats should havethe desired equivalent effect of constant regrinding the valve seat 38so as to always maintain a perfect fluidtight seal. FIG. 5 shows theprobable angle of the reactive forces tending to rotate the core 16 whenfluid is being discharged through the ports 82. I

Another type of valve core 16A is illustrated in FIG. 6. In this type,the discharge ports 83 are truly radial. This type of core is somewhateasier and less expensive to make than the type with the offsetdischarge ports. An inverted cup type of valve tip 39A may be formed onthe core 16A being adapted to seat on a flat valve seat. A valve tip ofthe 39A type could be used on any of the valve cores herein illustrateddepending on the particular application of the valve.

If on the other hand, a valve tip like 39 is used on the core 16A arelatively soft or pliant seat such as one made of Teflon may beutilized. In such case, the resiliency of the seat may be sufficient tomaintain a suitable fluidtight seal, or if the seat is made up in theform of an insert, it can be replaced periodically as required.

A most preferred embodiment for the valve core is shown in FIG. 8, andis designated by the numeral 168. The core 163 has a body 90 and isformed with an axial bore 91 and radially offset discharged ports 92similar to the ports 82 of FIGS. 4 and 5 which communicate with bore 91.The body 90 is also formed with an annular reduced portion 93 to form ineffect a wide groove giving the core 168 the appearance of a spool. Avalve tip 398 that is hemispherical in shape may replace the tapered tip39. A pair of semicircular sleeves 95 and 96 surround the reducedportion 93. The cross section of the sleeves 95 and 96 is shown bysuperimposed dotted lines in FIG. 8. The sleeves 95 and 96 are madeofvery high penneability material, and their axial length is slightly lessthan that of the length of the reduced portion 93. The sleeves areallowed to slide up and down along the reduced portion 93 and provide alight impact force against the lands- 97 and 98 for seating andunseating the core 168 whenever the solenoid 17 is actuated or cut off.The hemispherical tip 39B cooperates with a seat 99 having a low degreeof taper to provide a fluidtight seal. The spherical form provides aseal regardless of any slight angular misalignment of the axis of thecore 16B with the axis of tube 15.

It will be appreciated that thesernicir'cular sleeve feature can be usedwith valve cores having either radially ofl'set passages or truly radialpassages or a slightly tapered or hemispherical valve tip or theinverted cup type of valve tip.

Referring back to FIG. 1, the outlet control valve 12 comprises acylindrical tube of nonmagnetic material, a valve core 116, a solenoid117, and a split-shell housing 118 surrounding the coil 117. An axiallyextending cylindrical fitting 120 formed with an axially extending bore121 is attached to the upper end of tube 115 in fluid-sealed relationtherewith, and the upper end of the bore 121is in communication with thebore 52 and provides an inlet port 1130. to the valve 12. A cylindricalfitting 137 at the lower end of tube 115 is formed with an axial centralbore'or orifice 138 which also provides at its upper end a valve seatfor the valve tip 139. A fitting 124 provides an outlet port 140 for thevalve 12. The fitting 137 may be press-fitted into the tube 115 andsecured therein by a plurality of shear pins 141 extending through tube115 and into fitting 137. These pins 141 may be tubular in structure.The construction and operation of the valve 12 is substantially the sameas the valve 11, most of theparts being interchangeable. I

A compression spring of the same type as used in valve 11 may be used tohelp maintain the valve core 116 in a normally seated position and toovercome any residual magnetic effects when the solenoid 1 17 isdeenergized.

A fluid-pressure-responsive mechanism that may be controlled by thevalve assembly 10 is shown in longitudinal section in FIG. 9 and isdesignated by the numeral 200. The mechanism 200 comprises a housing 201fonned with an internal bore 202, a fixed sleeve 203, a spool valve 204,a piston 205, and a plunger 206. Cover plates 207 and 208 are bolted tothe ends of the housing 201 and are provided with fluid inlet ports 209and 210, respectively. The housing 201 is provided with radial ports211, 212, 213, 214 and 215. The ports 210 and 21 1 are connected throughsuitable conduits to a common high-pressure fluid source (not shown).The port 209 is connected through conduit 216 to fitting 56 of the valveblock 44. The ports214 and 215 are connected to power cylinders A and B(not shown), and the ports 212 and 213 exhaust to a fluid sump (notshown).

The valve sleeve 203 is formed with a central bore 220 in which thespool valve 204 is disposed, annular grooves 221, 222 and 223, andradial ports 224,225 and 226. The groove 221 communicates with the port'214, the groove 222 with port 211, and groove 223 with port 215. Theports 224, 225 and 226 all open into the bore 220 and are connected tothe annular grooves'221, 222 and 223, respectively.

The spool valve 204 is formed with lands 230 and 231 and an elongatedannular groove 232 between the lands. The lands 230 and 231 block theports 224 and 226, respectively, as shown. The piston 205 contacts theupper end 233 of the valve 204, and the plunger 206 contacts the lowerend 234 of valve 204. The spool valve 204 is movable longitudinallyunder the influence of fluid pressure between two limits. The upperlimit is reached when the piston 205 contacts the end plate 207,

- and the lower limit when the land 231 contacts the inner end 235 ofthe cover plate 208.

In operation, the valve assembly 10 and hydraulic mechanism 200 functionas follows. Relatively low pressure fluid or signal pressure is suppliedto the inlet port 30 of valve 11, and when the solenoid 17 is actuatedthe core 16 and tip 39 is raised off the seat 38 allowing the fluid topass through the outlet port 40, channel 54 and conduit 216 to the port209. The spool valve 204 and piston 205 will be in their uppermostposition until such signal pressure is supplied because of the forcedeveloped by the high-pressure fluid supplied through port 210 andacting on plunger 206. In the uppermost position, high-pressure fluidsupplied through the port 211 passes through the port 225, through thegroove 232 and ports 224 and 214 to power cylinder A. Thecross-sectional area of the piston 205 is substantially greater than thecross-sectional area of the plunger 206, and when the signal pressuresupplied through port 209 reaches predetermined value, the total forceacting on piston 205 will be sufficient to force the valve spool 204downward to its lowermost limit 235. In this latter position,high-pressure fluid from the port 211 passes through the port 225,groove 232 and ports 226 and 215 to power cylinder B. Any residual fluidpressure in the power cylinder A is permitted to exhaust through theports 224 and 212.

When operative conditions require that valve 204 be shifted again, suchshift is accomplished by energizing solenoid 117. Energizing solenoid117 causes the core 116 and tip 139 to be raised off the seat 138.Opening of the valve 12 thus releases the pressure applied againstpiston 205 through port 209, conduit 216, port 130 and outlet port 140to a fluid sump (not shown). When this pressure has been reducedsufficiently, the force acting through plunger 206 forces. the valve 204and piston 205 to the uppermost position. in this position, highpressurefluid is again supplied to power cylinder A as previously described, andany residual fluid pressure in power cylinder B is exhausted throughport 215, groove 223 and ports 226 and 213 to sump.

The energization of the valves 11 and 12 can be selectively accomplishedmanually or automatically by providing a suitable sensing mechanismeffective to operate switches connected to the solenoids l7 and 1 17.

The improved solenoid actuated pilot valves of the present invention aredesigned to provide precise and continuous control over a signal fluidpressure which in turn can effectively control the application ofsubstantially higher pressure fluid. The valve cores of the pilotvalves, with their sliding sleeves of high-permeability material, areeasily seated and unseated with minimal magnetic force supplied by therespective solenoids because of the slight impact provided by thesliding sleeve. This impact is sufficient to overcome the staticfriction of the seated valve, and is helpful to maintain the valve seatin uniform shape, when reseating. In addition, the novel splitshellhousing for the solenoid provides a construction that is easilyassembled and effectively retained in place and also ef fective toprovide an efficient flux-return path for the magnetic field generatedby the solenoid.

It is to be understood that the embodiments shown and described are byway of example only and the invention is not to be considered as limitedthereto except insofar as the claims may be so limited.

I claim:

1. in a pilot-control valve the combination comprising:

a fluidtight tube of nonmagnetic material;

means defining an inlet port associated with one end of said tube andadapted to be connected to a source of relatively higher fluid pressure;

means defining an outlet port associated with the other end of said tubeand adapted to be connected to an environment of relatively lowerpressure;

a valve core of magnetic material slidably disposed within said tube andformed with an axial central bore and a plurality of radially offsetfluid discharge ports connected to said bore;

means defining a valve seat adjacent said outlet port and adapted to beclosed by said valve core; and

a solenoid surrounding said tube and effective when energized to liftsaid valve core away from said seat to permit the passage of fluidthrough said outlet port.

2. The combination of claim 1 wherein said valve core carries a valvetip adaptedvto form a fluid-tight seal with said valve seat.

3. The combination of claim 1 wherein said valve core carries a sleeveof high-permeability material that is effective to impart a slightimpact to the core on energization of said solenoid.

4. The combination of claim 2 wherein said tip is hemispherical in shapeand said seat is tapered to receive said tip.

5. The combination of claim 2 wherein said valve seat comprises aplastic material.

6. The combination of claim 3 wherein said sleeve comprises a pair ofsemicylindrical shells that surround said valve core, said shells havingan axial length less than that of said core.

7. in a solenoid-actuated pilot-control valve having an inlet portadapted to be connected to a source of relatively higher fluid pressureand an outlet port adapted to be connected to a region of relativelylower pressure the combination comprismg:

a fluidtight central tube assembly including a tube of nonmagneticmaterial, and means defining inlet and outlet ports at opposite ends ofsaid tube;

magnetically responsive valve means disposed within said tube andeffective to restrict the flow of fluid through said outlet port;

a solenoid surrounding said tube assembly and efi'ective when energizedto create a magnetic field to operate said valve means; and

a split-shell housing of a generally cylindrical configurationsurrounding said solenoid and made of magnetic material and split intotwo parts along an axis substantially parallel to the axis of saidsolenoid whereby an efficient fluxretum path for the magnetic fieldcreated by said solenoid isprovided.

8. The combination of claim 7 including an enlarged washer of magneticmaterial disposed at each end of said solenoid within said housing toretainsaid solenoid and provide a still more efiicient flux-return path.

9. The combination of claim 7 wherein said split-shell housing is in twohalves with each half having an outwardly flared axial opening which inthe valve forms an encircling shroud around said tube assembly.

10. The combination of claim 9 wherein:

said halves are formed with outwardly flared axial opening at both oftheir axial ends and both forming encircling shrouds around said tubeassembly; and

means defining a circular recess surrounding said tube assembly andadapted to receive one of said encircling shrouds.

11. The combination of claim 9 including a circular retaining meansadapted to be mounted in said tube assembly and formed with a circularrecess for receiving the other encircling shroud to thereby effectivelyclamp the two halves of said housing together.

12. The combination of claim 7 including:

a mounting block for mounting said valve therein, said block havingfluid passage means formed therein for communication with afluid-pressure-responsive mechanism;

threaded bore means formed in said mounting block for receiving saidvalve therein; and

threaded retaining means surrounding said tube assembly and engagingsaid threaded bore means to secure said valve in said mounting block.

13. A pilot-control valve assembly comprising:

a pair of solenoid-operated valves for controlling respectively theapplication of fluid pressure from a source to afluid-pressure-responsive mechanism and the release of said mountingblock is formed with two bores for securing;

therein the outlet end of one of said valves and the inlet end of theother valve.

15. The pilot control valve assembly of claim 13 wherein:

7 8 a said mounting block is fonned with two threaded bores for axissubstantially parallel to the axis of the solenoid; and securing thereinthe outlet end of one of said valves and said mounting block is formedwith two threaded bores for j the inlet end of the other valve; andfurther including securing therein the outlet end of one of said valvesand retaining nuts which surround the respective ends of said the inletend of the other valve, and further includes valves and are respectivelythreadably secured into said retaining nuts which Surround respectivelysaid end mounting block bores to secure said valves in said mountandSaid inlet end and are p i y threadably Secured i b'l' k, I into saidmounting block bores to secure said valves in 16. The pilot controlvalve assembly of claim 13 wherein: said 'fS l each valve includes asplit-shell housing of a generally cylin- The combmatlon clalm 2 said "P15 formed drical configuration surrounding the solenoid of eachwithaninvened cup cross section valve and made of magnetic material andsplit along an

1. In a pilot-control valve the combination comprising: a fluidtighttube of nonmagnetic material; means defining an inlet port associatedwith one end of said tube and adapted to be connected to a source ofrelatively higher fluid pressure; means defining an outlet portassociated with the other end of said tube and adapted to be connectedto an environment of relatively lower pressure; a valve core of magneticmaterial slidably disposed within said tube and formed with an axialcentral bore and a plurality of radially offset fluid discharge portsconnected to said bore; means defining a valve seat adjacent said outletport and adapted to be closed by said valve core; and a solenoidsurrounding said tube and effective when energized to lift said valvecore away from said seat to permit the passage of fluid through saidoutlet port.
 2. The combination of claim 1 wherein said valve corecarries a valve tip adapted to form a fluid-tight seal with said valveseat.
 3. The combination of claim 1 wherein said valve core carries asleeve of high-permeability material that is effective to impart aslight impact to the core on energization of said solenoid.
 4. Thecombination of claim 2 wherein said tip is hemispherical in shape andsaid seat is tapered to receive said tip.
 5. The combination of claim 2wherein said valve seat comprises a plastic material.
 6. The combinationof claim 3 wherein said sleeve comprises a pair of semicylindricalshells that surround said valve core, said shells having an axial lengthless than that of said core.
 7. In a solenoid-actuated pilot-controlvalve having an inlet port adapted to be connected to a source ofrelatively higher fluid pressure and an outlet port adapted to beconnected to a region of relatively lower pressure the combinationcomprising: a fluidtight central tube assembly including a tube ofnonmagnetic material, and means defining inlet and outlet ports atopposite ends of said tube; magnetically responsive valve means disposedwithin said tube and effective to restrict the flow of fluid throughsaid outlet port; a solenoid surrounding said tube assembly andeffective when energized to create a magnetic field to operate saidvalve means; and a split-shell housing of a generally cylindricalconfiguration surrounding said solenoid and made of magnetic materialand split into two parts along an axis substantially parallel to theaxis of said solenoid whereby an efficient flux-return path for themagnetic field created by said solenoid is provided.
 8. The combinationof claim 7 including an enlarged washer of magnetic material disposed ateach end of said solenoid within said housing to retain said solenoidand provide a still more efficient flux-return path.
 9. The combinationof claim 7 wherein said split-shell housing is in two halves with eachhalf having an outwardly flared axial opening which in the valve formsan encircling shroud around said tube assembly.
 10. The combination ofclaim 9 wherein: said halves are formed with outwardly flared axialopening at both of their axial ends and both forming encircling shroudsaround said tube assembly; and means defining a circular recesssurrounding said tube assembly and adapted to receive one of saidencircling shrouds.
 11. The combination of claim 9 including a circularretaining means adapted to be mounted in said tube assembly and formedwith a circular recess for receiving the other encircling shroud toThereby effectively clamp the two halves of said housing together. 12.The combination of claim 7 including: a mounting block for mounting saidvalve therein, said block having fluid passage means formed therein forcommunication with a fluid-pressure-responsive mechanism; threaded boremeans formed in said mounting block for receiving said valve therein;and threaded retaining means surrounding said tube assembly and engagingsaid threaded bore means to secure said valve in said mounting block.13. A pilot-control valve assembly comprising: a pair ofsolenoid-operated valves for controlling respectively the application offluid pressure from a source to a fluid-pressure-responsive mechanismand the release of fluid pressure from the fluid-pressure-responsivemechanism; a valve-mounting block for securing said two valves therein,said mounting block having fluid passage means therein for communicationwith the fluid-pressure-responsive mechanism; said valves being securedin said mounting block in such a manner that the outlet of one of saidvalves and the inlet of the other of said valves are in fluidcommunication with said mounting-block fluid-passage means.
 14. Thepilot control valve assembly of claim 13 wherein said mounting block isformed with two bores for securing therein the outlet end of one of saidvalves and the inlet end of the other valve.
 15. The pilot control valveassembly of claim 13 wherein: said mounting block is formed with twothreaded bores for securing therein the outlet end of one of said valvesand the inlet end of the other valve; and further including retainingnuts which surround the respective ends of said valves and arerespectively threadably secured into said mounting block bores to securesaid valves in said mounting block.
 16. The pilot control valve assemblyof claim 13 wherein: each valve includes a split-shell housing of agenerally cylindrical configuration surrounding the solenoid of eachvalve and made of magnetic material and split along an axissubstantially parallel to the axis of the solenoid; and said mountingblock is formed with two threaded bores for securing therein the outletend of one of said valves and the inlet end of the other valve, andfurther includes retaining nuts which surround respectively said outletend and said inlet end and are respectively threadably secured into saidmounting block bores to secure said valves in said mounting block. 17.The combination of claim 2 wherein said tip is formed with an invertedcup cross section.